erbert A. Simon, an American polymath who won the Nobel in economics in 1978 with a new theory of decision making and who helped pioneer the idea that computers can exhibit artificial intelligence that mirrors human thinking, died yesterday. He was 84.
He died at the Presbyterian University Hospital of Pittsburgh, according to an announcement by Carnegie Mellon University, which said the cause was complications after surgery last month. Mr. Simon was the Richard King Mellon University Professor of Computer Science and Psychology at the university — a title that underscored the breadth of his interests and learning.
Mr. Simon also won the A. M. Turing Award for his work on computer science in 1975 and the National Medal of Science in 1986. In 1993, he was awarded the American Psychological Association's award for outstanding lifetime contributions to psychology.
In 1994, he became one of only 14 foreign scientists ever to be inducted into the Chinese Academy of Sciences and in 1995 was given awards by the International Joint Conferences on Artificial Intelligence and the American Society of Public Administration.
Awarding him the Nobel, the Swedish Academy of Sciences cited "his pioneering research into the decision-making process within economic organizations" and acknowledged that "modern business economics and administrative research are largely based on Simon's ideas."
Professor Simon challenged the classical economic theory that economic behavior was essentially rational behavior in which decisions were made on the basis of all available information with a view to securing the optimum result possible for each decision maker.
Instead, Professor Simon contended that in today's complex world individuals cannot possibly process or even obtain all the information they need to make fully rational decisions. Rather, they try to make decisions that are good enough and that represent reasonable or acceptable outcomes.
He called this less ambitious view of human decision making "bounded rationality" or "intended rational behavior" and described the results it brought as "satisficing."
In his book "Administrative Behavior" he set out the implications of this approach, rejecting the notion of an omniscient "economic man" capable of making decisions that bring the greatest benefit possible and substituting instead the idea of "administrative man" who "satisfices — looks for a course of action that is satisfactory or `good enough.' "
Professor Simon's interest in decision making led him logically into the fields of computer science, psychology and political science. His belief that human decisions were made within clear constraints seemed to conform with the way that computers are programmed to resolve problems with defined parameters.
In the mid-1950's, he teamed up with Allen Newell of the Rand Corporation to study human decision making by trying to simulate it on computers, using a strategy he called thinking aloud.
People were asked for the general reasoning processes they went through as they solved logical problems and these were then converted into computer programs that Professor Simon and Mr. Newell thought equipped these machines with a kind of artificial intelligence that enabled them to simulate human thought rather than just perform stereotyped procedures.
The breakthrough came in December 1955 when Professor Simon and his colleague succeeded in writing a computer program that could prove mathematical theorems taken from the Bertrand Russell and Alfred North Whitehead classic on mathematical logic, "Principia Mathematica."
The following January, Professor Simon celebrated this discovery by walking into a class and announcing to his students, "Over the Christmas holiday, Al Newell and I invented a thinking machine."
A subsequent letter to Lord Russell explaining his achievement elicited the reply: "I am delighted to know that `Principia Mathematica' can now be done by machinery. I wish Whitehead and I had known of this possibility before we wasted 10 years doing it by hand."
But in a much-cited 1957 paper Professor Simon seemed to allow his own enthusiasm for artificial intelligence to run too far ahead of its more realistic possibilities. Within 10 years, he predicted, "a digital computer will be the world's chess champion unless the rules bar it from competition," while within the "visible future," he said, "machines that think, that learn and that create" will be able to handle challenges "coextensive with the range to which the human mind has been applied."
Sure enough, the I.B.M computer Deep Blue did finally beat the world chess champion Gary Kasparov last year — about three decades after Mr. Simon had predicted the event would occur.
Because artificial intelligence has not grown as quickly or as strongly as Professor Simon hoped, critics of his thinking argue that there are limits to what computers can achieve and that what they accomplish will always be a simulation of human thought, not creative thinking itself. As a result, Professor Simon's achievements have sparked a passionate and continuing debate about the differences between people and thinking machines.
Born on June 15, 1916, the son of German immigrants, in Milwaukee, Herbert A. Simon attended public school and entered the University of Chicago in 1933 with the intention of bringing the same rigorous methodology to the social sciences as existed in physics and other "hard" sciences.
As an undergraduate his interest in decision making was aroused when he made a field study of Milwaukee's recreation department. After receiving his bachelor's degree in 1936 he became an assistant to Clarence E. Ridley of the International City Managers Association and then continued work on administrative techniques in the Bureau of Public Administration of the University of California at Berkeley.
In 1942, he moved to the Illinois Institute of Technology and in 1943 received his doctorate from the University of Chicago for a dissertation subsequently published in 1947 as "Administrative Behavior: A Study of Decision-Making Processes in Administrative Organizations."
In 1937, he married Dorothea Pye, who survives him along with three children, Katherine Simon Frank of Minneapolis; Peter A. Simon of Bryan, Tex.; and Barbara M. Simon of Wilder, Vt.; six grandchildren, three step-grandchildren; and five great- grandchildren.
A member of the faculty of Carnegie Mellon University since 1949, Professor Simon played important roles in the formation of several departments and schools including the Graduate School of Industrial Administration, the School of Computer Science and the College of Humanities and Social Sciences' psychology department.
He published 27 books, of which the best known today are "Models of Bounded Rationality" (1997), "Sciences of the Artificial"(1996) and "Administrative Behavior"(1997).
In 1991 he published his autobiography, "Models of My Life," and remarked then about his vision of that all-vanquishing computer hunched over the chess boards of the world: "I still feel good about my prediction. Only the time frame was a bit short." And so it was.